经典sql语句

一、循环
create table tb(
   col1 varchar(1),
   col2 varchar(2)
) 
insert tb(col1,col2)values('0','0')
 go 10000000
二、数据合并
if object_id('[order]') is not null drop table [order]
go
create table [order]([orderid] int,[ordertype] varchar(1))
insert [order]
select 1,'A' union all
select 2,'B'
if object_id('[order_car]') is not null drop table [order_car]
go
create table [order_car]([orderid] int,[carno] varchar(100))
insert [order_car]
select 1,'10' union all
select 1,'20' union all
select 2,'30'
select
  b.orderid,
  a.ordertype,
  carno=stuff((select ','+ltrim(carno) from order_car where orderid=b.orderid for xml path('')),1,1,'')
from
  [order] a
join
  order_car b
on
  a.orderid=b.orderid
group by
  b.orderid,
  a.ordertype